JP2594984B2 - Moisture separator drain tank water level controller - Google Patents

Description

The present invention relates to a water level control device for a moisture separator drain tank of an electronic power plant, and more particularly to a case where a digital control device is employed as a control arithmetic device. It relates to improvement of control calculation.

[Conventional technology]

To improve the reliability of the control device for the moisture separator drain tank, there is already a flow control device disclosed in Japanese Utility Model Publication No. 61-9208.
A monitoring device that monitors the control signal to the service control valve and the control signal to the emergency control valve is provided, and when an abnormality of the control signal is detected, another control signal is introduced. .

[Problems to be solved by the invention]

In the above prior art, a service water level control system and an emergency water level control system are provided as a water level control device of the moisture separator drain tank, but the control system includes a signal generator for generating a level signal of the drain tank and an adjustment valve. This is for a simple control system composed of the same control valve (same as a control valve), and when the control signal is abnormal, the other control signal is introduced to continue the control and improve the reliability of the control system. In this control system, the water level control area of the drain tank is the drain flow rate (m ³ / H)
This is effective when the load is large enough, or when the load change speed is slow and the water level change in the drain tank is slow, but the drain tank actually used in the nuclear power plant is designed in consideration of economy. In many cases, the capacity is relatively small (the water level control area is relatively small), and the control system is a water level transmitter (a signal generator that generates a level signal for the drain tank) and a control valve. In many cases, a control arithmetic unit is provided for performing a control operation in response to a water level signal from a control signal, and the output signal controls the control valve. 61-92
No. 08 discloses a signal transmission cut-off device (isolation valve) for each control signal line and a tie line between both control systems so that the control signals of the service level control system and the emergency water level control system can be mutually backed up. A signal transmission blocking device is also provided on the line. This prior art focuses solely on providing a mutual back-up function between the service system and the emergency system, and does not consider controllability when switching the control system in the event of an abnormality. It is assumed that there is a problem. In addition, the configuration of the control device is simple, and it is considered that the design margin for the controllability on the drain tank side needs to be sufficient to apply this.

An object of the present invention is to provide a water level control system in which each water level control system is composed of a water level transmitter, a control arithmetic unit, and a control valve of a drain tank. An object of the present invention is to provide a moisture separator drain tank water level control device.

[Means for solving the problem]

As a measure for improving the reliability of the control system, there is a multiplexing method. However, in the case of multiplexing, construction costs are increased and maintenance costs are also increased. In order to improve the reliability of a highly economical nuclear power plant, it is particularly effective to improve the functions of the facilities at present. When a digital control device is used as the control calculation device, the function can be improved by improving and enhancing the software (control calculation method). The present invention intends to further enhance the backup function of the emergency water level control system of the moisture separator drain tank by enriching the software. The emergency control arithmetic unit is provided with a water level signal from the emergency water level transmitter. A function for diagnosing the input signal abnormality is added to judge whether or not the input signal is abnormal.When the input signal is abnormal, the water level signal is accepted from the service control arithmetic unit. This is achieved by creating an open signal and adding a function of making this signal the output of the emergency control arithmetic unit instead of the control arithmetic output by the input signal from the emergency water level transmitter.

In addition, for the service level control system of the moisture separator drain tank, an input signal abnormality diagnosis function to determine whether the level signal from the service level transmitter is abnormal is added to the service control arithmetic unit, and the When the signal is abnormal, the water level signal is received from the emergency control operation unit, the emergency system water level signal is corrected to the service level signal, and this is used as a substitute for the input signal from the service level transmitter, and the control operation is performed. And a function to output the output from the common control arithmetic unit.

[Action]

The primary purpose of the emergency water level control system of the moisture separator drain tank is to detect the rise in water level of the drain tank and open the emergency control valve when the water level of the drain tank rises due to failure of the service control valve. Becomes This is because when the water level in the moisture separator drain tank rises excessively and the "high water level" of the moisture separator is detected, the shut-off valve at the low-pressure turbine inlet is closed to prevent water from flowing into the turbine, and the turbine is tripped ( This is because the water level in the drain tank must be avoided. Normally, the emergency water level control system controls the water level by setting a control target value at a control level (DWL) slightly higher than the control level (NWL) of the normal system, but the water level signal from the emergency water level transmitter is abnormal. In the case of, the water level signal (detected by the service level transmitter) is accepted from the service control arithmetic unit, and the water level signal is within the water level detection range of the service level transmitter, regardless of the DWL. When the value reaches or exceeds the upper limit, a signal for opening the emergency control valve is generated, and this signal is given to the control valve. At this time, for example, by making a signal that changes the emergency control valve from fully closed to fully open at the upper limit 50 mm of the detection range of the service water level transmitter, even if the emergency water level transmitter becomes abnormal In addition, it is possible to add a function of "opening the emergency control valve when the water level rises", which is the main purpose of the emergency water level control system, thereby preventing an excessive rise in the water level of the drain tank.

Also, when the water level signal of the service level control system of the moisture separator drain tank becomes abnormal, the water level signal (signal from the emergency water level transmitter) is accepted from the emergency control arithmetic unit, and the emergency system water level is received. The signal is corrected to the service level signal, and this is used as a substitute for the input signal from the service level transmitter,
The control operation is performed to control the service control valve as an output of the service control calculator. In this case, the control target value, controllability and the like are slightly affected by the difference in the detection range between the service level transmitter and the emergency water level transmitter. Part of the control can be performed by taking the part into the service level control system, so that the control by the service control valve can be continued almost normally even when the service level transmitter is abnormal.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic piping system diagram relating to a water level control device of a moisture separator drain tank of a nuclear power plant which is a field of application of the present invention, and FIGS. 2 and 3 are block diagrams of a control arithmetic unit. .

The outline of the water level control device of the moisture separator drain tank will be described with reference to FIG. Steam is generated in the Atsushi furnace 1 and sent to the high-pressure turbine 3 via the main steam pipe 2 for work. Since the discharged steam is wet steam, the steam is sent to the moisture separator 5 through the steam pipe 4 to perform steam-water separation. The separated drain is collected in a moisture separator drain tank 6. On the other hand, the steam from which the moisture has been reduced is sent to the low-pressure turbine 7 to perform the work again. The high-pressure turbine 3 and the low-pressure turbine 7 include a generator 8
Turn to generate electricity. The steam that has finished work in the low-pressure turbine 7 is cooled by the condenser 10 and becomes ascites. This condensed water is pressurized by a condensate pump 12 installed in a condensate pipe 11 and sent to a low-pressure feed water heater 13 (three or four units are often installed in series) to extract air from the low-pressure turbine 7 (not shown). To heat. This condensed water is further pressurized by a water supply pump 14 and sent to a high-pressure water heater 16 (in many cases, two or three units are connected in series), and is heated by bleed air from the high-pressure turbine 3 or discharged steam (not shown). Then, water is supplied as water to the reactor 1 via the water supply pipe 15.

On the other hand, the drain collected in the moisture separator drain tank 6 is sent to the low-pressure feed water heater 13 through the common drain pipe 21 to heat the condensate. In an emergency, the condenser 10 is connected to an emergency drain pipe 31 branched from the service drain pipe 21.
It has a configuration that allows drainage.

If the moisture separator drain tank 6 becomes empty, the steam of the moisture separator 5 will flow to the low-pressure feed water heater 13 and the thermal efficiency of the plant will be reduced. To prevent this, the water level is generally maintained at a specified level. As the water level is controlled.

For this reason, the following device is installed as a water level control device of the moisture separator drain tank 6 as shown in FIG. In other words, to detect the normal operating water level, the service level transmitter
41 is provided, and sends the detected water level as a water level signal 42 to the service control arithmetic unit 43. Here, control calculation is performed so as to maintain the specified water level (NWL), and a valve opening command signal 45 is output. Based on this signal, the service control valve 22 installed in the service drain pipe 21
Open / close control. Should the water level rise abnormally,
Emergency water level transmitter 5 to maintain the water level at the specified water level (DWC)
The water level is detected by 1 and the control operation is performed by the emergency control calculator 53 based on the water level signal 52 to output a valve opening command signal 55,
The opening / closing control of the emergency control valve 32 installed in the emergency drain pipe 31 is performed. The service control operation unit 43 and the emergency control operation unit 53 may be separately installed as hardware.However, in recent years, with the development of digital control devices, both have been prepared as one piece of hardware like a framework at 61. , Regular control computing unit 43 and emergency control computing unit as software programs
In some cases, 53 functions are provided. The present invention embraces both, but for ease of explanation,
In the following description, the regular control computing unit 43 and the emergency control computing unit 53 are regarded as separate entities.

FIGS. 2 and 3 are control block diagrams of the emergency control operation unit 53 and the service control operation unit 43 of FIG. 1, and show one embodiment of the present invention.

FIG. 2 is a control block diagram of the emergency control arithmetic unit 53. The water level signal 52 of the emergency water level transmitter 51 is input, and a sensor check 53.1 having an input signal abnormality diagnosis function determines whether there is an abnormality in the input signal. In recent digital control devices, the abnormality of the input signal is often judged based on the fact that the input signal is out of the specified range or the rate of change between the sampling times is excessive. When the input signal is normal, the signal after sensor check is 52.1
Is taken into the error calculator 53.2, the deviation from the set value (not shown) is calculated, the proportional, integral, and differential operations are performed by the control calculator 53.3, and the emergency is calculated via the switch 53.4 and the manual / automatic switch 53.5. A valve opening command signal 55 is provided to the emergency control valve 32 as an output of the control arithmetic unit 53. In the conventional technology, when an abnormality is detected by the sensor check 53.1, the control calculation is stopped, and
It has been common practice to keep the valve opening command signal 55 at the current value, or to output a signal for fully opening the control valve.
On the other hand, in the present invention, the water level signal 42 from the service level transmitter 41 is input as the service level signal 54 after the sensor check from the service control calculator 43 (see FIG. 3), and this is input to the function calculator. The valve opening command signal 54.1 is generated according to 53.6, and if an abnormality is detected by the sensor check 53.1, the switch 53.4
From the output signal 52.2 of the control calculator 53.3, the function calculator 53.6
Output signal 54.1. FIG. 4 shows an example of a characteristic diagram of the function calculator 53.6. The detection range of the service level transmitter 41 is NWL ± 250 mm, and the control target value (D
WL) is set to NWL + 200 mm, and the function calculator (f ₂ (x)) 53.6 starts to open the valve at NWL + 200 mm (DWL) and outputs a signal to fully open the valve at NWL + 250 mm. According to the present embodiment, even when the input signal from the emergency water level transmitter 51 is abnormal, the water level is DW.
When the water level rises above L, the emergency control valve 32 can be opened, which has the effect of preventing the water level from rising excessively. In this case, since the control gain for the emergency control valve 32 generally tends to be excessive, the control valve often switches the opening / closing operation in response to the fluctuation of the water level, but this is the original function as the emergency system. It works effectively to prevent abnormal rise of water level.

FIG. 3 is a control block diagram of the service control arithmetic unit 43.
The water level signal 42 of the service level transmitter 41 is input, and the sensor check 43.1 having an input signal abnormality diagnosis function determines whether or not the input signal is abnormal. Normally, the input signal is sent to a deviation calculator 43.2 via a switch 43.4 after a sensor check, and a deviation from a set value (not shown) is obtained.
Then, the operation of proportional, integral, and differential operations is performed, and a valve opening command signal 45 is supplied to the service control valve 22 as an output of the service control calculator 43 via a manual / automatic switch 43.5. In the related art, when an abnormality is detected by the sensor check 43.1, the control calculation is stopped and the valve opening command signal 45 is maintained at the current value, or a signal for completely closing the control valve is output. Was common. On the other hand, in the present invention, the water level signal 52 from the emergency water level transmitter 51 is input as the emergency water level signal 44 after the sensor check from the emergency control arithmetic unit 53 (see FIG. 2). The water level signal of the service system by the arithmetic unit 43.6
Create a signal 44.1 at the same level as 42.1, and
When an abnormality is detected in 3.1, the switching unit 43.4 switches from the normal system water level signal 42.1 to the output signal 44.1 of the function operation unit 43.6. FIG. 5 shows an example of a characteristic diagram of the function calculator 43.6. The detection range of the emergency water level transmitter 51 When the detection range of the service level transmitter 41 is NWL ± 250 mm,
Input signal 0 to 41.7% (water level NWL-250mm to NWL + 250mm) is converted to output signal 0 to 100% and output. According to the present embodiment, since the water level signal 44 from the emergency control arithmetic unit 53 can be converted into a signal of exactly the same level as the signal from the service level transmitter 41, the input signal from the service level transmitter 41 Even in the case of an abnormality, control equivalent to that in the normal state can be continued by signal switching.

In FIG. 2 and FIG. 3, the backup signal when the input signal is abnormal is inputted from the service control operation unit 43 and the emergency control operation unit 53, but the service level transmitter 41 and the emergency level transmitter are used.
You can also input directly from 51.

2 and 3, the deviation calculators 53.2, 43.
2. Although the description has been made assuming individual values as in the control arithmetic units 53.3 and 43.3, when these arithmetic processes are performed by a software program, the arithmetic functions thereof are expressed.

〔The invention's effect〕

According to the present invention, even when the signal from the emergency water level transmitter becomes abnormal, the control can be continued as it is, and if the water level rises, the emergency control valve should be opened. Therefore, it is possible to prevent an excessive rise in water level, and to prevent turbine trip (leading to a reactor scram) due to a high water level of the moisture separator. Further, even when the signal from the service level water transmitter becomes abnormal, the control can be continued as it is. These effects are generally achieved by duplicating the emergency water level transmitter and the service water level transmitter. However, according to the present invention, the service program of the service control processor and the emergency control processor is strengthened by strengthening the software program. This can be achieved.

[Brief description of the drawings]

1 is a system diagram of a water level control device according to one embodiment of the present invention, FIGS. 2 and 3 are control block diagrams of the present invention, and FIGS. 4 and 5 are characteristics of a function calculator in the embodiment. FIG. 6… Drain tank for moisture separator, 22… Service control valve, 32… Emergency control valve, 41… Service water level transmitter, 43… Service control calculator, 51… Emergency water level transmitter, 53 ... Emergency control computing unit.

Claims (2)

(57) [Claims] A service level transmitter for detecting a water level in a moisture separator drain tank of a nuclear power plant and generating a water level signal; a service control arithmetic unit for receiving and controlling the water level signal; A service level control system including a service control valve for adjusting a valve opening based on an output signal of a service control arithmetic unit, and an emergency water level transmitter for detecting a water level of the moisture separator drain tank and generating a water level signal An emergency water level control device including an emergency control arithmetic unit that performs a control operation in response to the water level signal, and an emergency control valve that adjusts a valve opening degree based on an output signal of the emergency control arithmetic unit. The emergency control arithmetic unit has an input signal abnormality diagnosis function for determining whether or not the water level signal from the emergency water level transmitter is abnormal, and when the input signal is abnormal, accepts a water level signal from the service level control system. ,That When the water level signal reaches or exceeds the present fixed value, a signal for opening the emergency control valve is generated, and this signal is used instead of the control operation output by the input signal from the emergency water level transmitter. A water level control device for the drain tank of a moisture separator characterized by adding a function to output. 2. An apparatus for controlling a water level of a drain tank of a moisture separator according to claim 1, wherein the input for judging whether or not a water level signal from said normal water level transmitter is abnormal is input to said normal control arithmetic unit. A signal abnormality diagnosis function is added, and when an input signal is abnormal, a water level signal is received from the emergency water level control system and corrected to a service level signal, and this is adopted as a substitute for the input signal from the service level transmitter. And a function of performing a control operation and outputting the output of the common control operation unit.